Olefin–Borane “van der Waals Complexes”: Intermediates in Frustrated Lewis Pair Addition Reactions

The nature of the borane–olefin interactions that take place prior to frustrated Lewis pair addition reactions has been probed employing a Lewis acidic borane tethered to a vinyl group through an alkyl chain. 1H{19F} HOESY spectral data obtained at −50 °C demonstrated the spatial proximity of the boryl and vinyl groups and computational data support the initial formation of a van der Waals borane–olefin complex. Such species serve as intermediates undergoing facile addition reactions with phosphine bases to afford cyclic zwitterionic products

Contrasting Formation of a (Phenylthio)phosphinimine and (Phenylthio)phosphazide. Synthesis of Metal Complexes

Contrasting Formation of a (Phenylthio)phosphinimine and (Phenylthio)phosphazide. Synthesis of Metal Complexe

Phosphines Bearing Alkyne Substituents: Synthesis and Hydrophosphination Polymerization

A synthetic route is described for a series of phosphines bearing pendant alkyne substituents, from the conversion of BrC6H2R2CCR′ (R = Me, i-Pr; R′ = Ph, SiMe3) to [(μ-Br)Cu(Et2N)2PC6H2R2CCR′]2 and subsequently to Cl2PC6H2R2CCR′ and H2PC6H2R2CCR′. Lithiation and subsequent alkylation yield the secondary phosphines R(H)PC6H2(i-Pr)2CCPh (R = CH2i-Pr, CH2Ph). Intermolecular hydrophosphination−polymerization is used to prepare the polymeric species [RPC6H2(i-Pr)2CHCPh]n, which can then be sulfurized to give [RP(S)C6H2(i-Pr)2CHCPh]n. The polymeric products were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and gel permeation chromatography. These data indicate a degree of polymerization (DPn) of up to 60. Discussion of the mechanism is augmented with gas-phase density functional theory calculations

Structural Isomers of the Chromium Bis(phosphoranimine)methanide Complex [(HC(PPh₂NSiMe₃)₂)Cr(μ-Cl)]₂

The species [(HC(PPh2NSiMe3)2Cr(μ-Cl)2] was prepared and structurally characterized. It is shown to exist in two structural isomers:  one in which the Cr center adopts a pseudo-square-planar coordination geometry and another where the metal coordination sphere is better described as trigonal bipyramidal. Preliminary assessment of the catalytic activity in ethylene polymerization is also reported

Room Temperature Reduction of CO₂ to Methanol by Al-Based Frustrated Lewis Pairs and Ammonia Borane

Room Temperature Reduction of CO2 to Methanol by Al-Based Frustrated Lewis Pairs and Ammonia Boran

Stoichiometric Metal-Free Reduction of CO in Syn-Gas

Reaction of a 2:1 mixture of B­(C6F5)3 and tBu3P with syn-gas results in the stoichiometric reduction of CO to give a formyl derivative which reacts further via an epoxy-borate intermediate to capture CO, affording a heterocylic alkoxyborate. Heating the reaction prompts reaction with H2 to give a borane-oxy-borate derivative, the product of C–O bond cleavage

Ruthenium and Rhodium Complexes of Thioether-Alkynylborates

The species ((C6F5)2BCH2SPh)2 reacts with PhCCLi to give the thioether-alkynylborate (C6F5)2BCH2SPh­(CCPh)­Li­(THF)2 (1). Subsequent reaction with (Ph3P)3RuHCl, (Ph3P)3RhCl, and [(COD)­Rh­(μ-Cl)]2 gives (C6F5)2BCH2SPh­(CCPh)­RuH­(PPh3)2 (2), (C6F5)2BCH2SPh­(CCPh)­Rh­(PPh3)2 (4), and (C6F5)2BCH2SPh­(CCPh)­Rh­(COD) (5), respectively, demonstrating a bidentate binding mode via the alkynyl and thioether donors of the borate. Subsequent reactions of 2 and 4 with H2 gave (C6F5)2BCH2SPh­(CH2CH2Ph)­RuH­(PPh3)2 (3) and ((C6F5)2BCH2SPh­(CHCHPh))­Rh­(PPh3)2 (6). In the former case, the borate remains bound to the metal via a π-interaction with the thioether-arene ring, while in the latter case, S and alkene binding is observed

Salts of the Cation [(Cp*Cr)₄(μ-Cl)₃(μ-CH₂)₃AlMe]⁺ with the Oxo- and Methine-Based Aluminum Anions [(Me₂Al)₂(μ-CH)(AlCl₂Me)₂]^- and [(Me₂Al)(μ₃-O)(AlCl₂Me)(AlMe₂Cl)]^-

Reactions of (Cp*CrCl2)2 (1) and Cp*Cr(HNP-i-Pr3)Cl2 (3) with excess AlMe3 gave [(Cp*Cr)4(μ-Cl)3(μ-CH2)3AlMe][(Me2Al)(μ3-O)(AlCl2Me)(AlMe2Cl)] (2) and [(Cp*Cr)4(μ-Cl)3(μ-CH2)3AlMe][(Me2Al)2(μ-CH)(AlCl2Me)2] (4), respectively. Although the cations are the same, the former salt has a Al3O-based anion, whereas the latter contains an Al4−methine anion

Three-Coordinate, Cyclic Bent Allene Iron Complexes

Novel three-coordinate Fe complexes featuring 1,2-diphenyl-3,5-bis­(2,6-dimethylphenoxy)­pyrazolin-4-ylidine or “cyclic bent allene” (CBA) have been synthesized. Reaction with FeCl2(PPh3)2 results in the loss of both phosphines to yield monomeric Fe­(CBA)­Cl2. Treatment with 2 equiv of benzyl Grignard affords the three-coordinate alkylated product Fe­(CBA)­(Bn)2. Exposure of the alkylated species to an atmosphere of CO results in reductive elimination of 1,3-diphenylpropanone and formation of trigonal-bipyramidal Fe­(CBA)­(CO)4

Room Temperature Reduction of CO₂ to Methanol by Al-Based Frustrated Lewis Pairs and Ammonia Borane

Room Temperature Reduction of CO2 to Methanol by Al-Based Frustrated Lewis Pairs and Ammonia Boran